1. Field of the Invention
The present invention relates generally to high intensity, solid state lighting devices. More particularly, the invention relates to the use of a primarily axial thermal dissipation system to provide for a compact, high intensity, solid state lighting device with a predominantly axial overall form factor.
The present invention further relates to the use of a primarily axial thermal dissipation system to provide for a compact, high intensity, solid state lighting device with a comparatively low profile overall form factor.
2. Background Information
High intensity light sources are widely used in projection systems, television backlights, automotive headlamps and other devices that require a relatively compact, high output light source. Some applications require a high intensity light source with limited Etendue (the product of light source area and solid-angle of light output). For these applications, the light emitting source itself must be as small as possible to achieve the highest efficiencies. Furthermore, some of these applications may have the additional requirement for a lighting device with a particular overall form factor, such as a predominately axial (long and slender) form factor, or alternatively, a comparatively low profile (thin and wide) form factor. Examples of applications that require an illumination source with limited Etendue and a particularly demanding device form factor are ultra-compact image projectors, surgical headlights and hand held light curing wands.
Generally, High Intensity Discharge (HID) lamps have been used heretofore in high intensity light sources due to their high photonic output and high photonic conversion efficiencies. In operation, however, these devices are hindered by relatively short operating lifetimes, erratic performance, catastrophic failure that can interfere with automatic or man-life dependent operations and the production of high levels of radiated and convected waste heat which can negatively affect the objects of illumination. In addition, applications that require a lighting device with a particularly compact or otherwise demanding form factor may require supplementary light guide structures, such as fiber optics, in order to locate the light source remotely, relative to the object of illumination.
As products that require light sources have become increasingly compact and in many cases more portable, the need has arisen for compact, reliable, solid state illumination sources. These sources, typically based on Light Emitting Diode (LED) technology, offer longer operating lifetimes, predictable performance, more predictable and manageable failure modes and tunable spectral output. In addition, the waste heat generated by an LED is primarily conductive in nature and with proper design, can be dissipated with little or no affect on the object of illumination.
A major shortcoming of the current state of the art of LED technology, however, is its inability to produce adequate levels of illumination in applications that require a high intensity lighting device with a particularly demanding overall form factor, such as a compact, predominately axial form factor or a compact, low profile form factor. These devices lack the required thermal dissipation mechanisms to adequately eliminate the waste heat that is being generated. This is especially true for applications that require a limited Etendue. For these applications, the LED dies must be grouped into closely spaced arrays. This close spacing results in a large thermal flux, exacerbating the thermal dissipation challenges.
It is therefore a principal object of the present invention to provide a high intensity, solid state lighting apparatus that is characterized by its ability to dissipate a large thermal flux while maintaining a compact, predominately axial form factor.
It is a further object of the present invention to provide a high intensity, solid state lighting apparatus that is characterized by its ability to dissipate a large thermal flux while maintaining a compact, low profile form factor.